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Register a new userDevelopment and Parameters of a Non-Self-Similar CME Caused by Eruption of a Quiescent Prominence
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The eruption of a large quiescent prominence on 17 August 2013 and associated coronal mass ejection (CME) were observed from different vantage points by Solar Dynamics Observatory (SDO), Solar-Terrestrial Relations Observatory (STEREO), and Solar and Heliospheric Observatory (SOHO). Screening of the quiet Sun by the prominence produced an isolated negative microwave burst. We estimated parameters of the erupting prominence from a model of radio absorption and measured from 304 AA images. Their variations obtained by both methods are similar and agree within a factor of two. The CME development was studied from the kinematics of the front and different components of the core and their structural changes. The results are verified using movies in which the CME expansion was compensated according to the measured kinematics. We found that the CME mass ($3.6 times 10^{15}$ g) was mainly supplied by the prominence ($approx 6 times 10^{15}$ g), while a considerable part drained back. The mass of the coronal-temperature component did not exceed $10^{15}$ g. The CME was initiated by the erupting prominence, which constituted its core and remained active. The structural and kinematical changes started in the core and propagated outward. The CME structures continued to form during expansion, which did not become self-similar up to $25 R_odot$. The aerodynamic drag was insignificant. The core formed until $4 R_odot$. Some of its components were observed to straighten and stretch forward, indicating the transformation of tangled structures of the core into a simpler flux rope, which grew and filled the cavity as the CME expanded.
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Context. Prominence eruptions provide key observations to understand the launch of coronal mass ejections as their cold plasma traces a part of the unstable magnetic configuration. Aims. We select a well observed case to derive observational constraints for eruption models. Methods. We analyze the prominence eruption and loop expansion and contraction observed on 02 March 2015 associated with a GOES M3.7 class flare (SOL2015-03-02T15:27) using the data from Atmospheric Imaging Assembly (AIA) and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). We study the prominence eruption and the evolution of loops using the time-distance techniques. Results. The source region is a decaying bipolar active region where magnetic flux cancellation is present for several days before the eruption. AIA observations locate the erupting prominence within a flux rope viewed along its local axis direction. We identify and quantify the motion of loops in contraction and expansion located on the side of the erupting flux rope. Finally, RHESSI hard X-ray observations identify the loop top and two foot-point sources. Conclusions. Both AIA and RHESSI observations support the standard model of eruptive flares. The contraction occurs 19 minutes after the start of the prominence eruption indicating that this contraction is not associated with the eruption driver. Rather, this prominence eruption is compatible with an unstable flux rope where the contraction and expansion of the lateral loop is the consequence of a side vortex developing after the flux rope is launched.
Coronal implosions - the convergence motion of plasmas and entrained magnetic field in the corona due to a reduction in magnetic pressure - can help to locate and track sites of magnetic energy release or redistribution during solar flares and eruptions. We report here on the analysis of a well-observed implosion in the form of an arcade contraction associated with a filament eruption, during the C3.5 flare SOL2013-06-19T07:29. A sequence of events including magnetic flux-rope instability and distortion, followed by filament eruption and arcade implosion, lead us to conclude that the implosion arises from the transfer of magnetic energy from beneath the arcade as part of the global magnetic instability, rather than due to local magnetic energy dissipation in the flare. The observed net contraction of the imploding loops, which is found also in nonlinear force-free field extrapolations, reflects a permanent reduction of magnetic energy underneath the arcade. This event shows that, in addition to resulting in expansion or eruption of overlying field, flux-rope instability can also simultaneously implode unopened field due to magnetic energy transfer. It demonstrates the partial opening of the field scenario, which is one of the ways in 3D to produce a magnetic eruption without violating the Aly-Sturrock hypothesis. In the framework of this observation we also propose a unification of three main concepts for active region magnetic evolution, namely the metastable eruption model, the implosion conjecture, and the standard CSHKP flare model.
We study a sequence of eruptive events including filament eruption, a GOES C4.3 flare and a coronal mass ejection. We aim to identify the possible trigger(s) and precursor(s) of the filament destabilisation; investigate flare kernel characteristics; flare ribbons/kernels formation and evolution; study the interrelation of the filament-eruption/flare/coronal-mass-ejection phenomena as part of the integral active-region magnetic field configuration; determine Halpha line profile evolution during the eruptive phenomena. Multi-instrument observations are analysed including Halpha line profiles, speckle images at Halpha-0.8 AA and Halpha+0.8 AA from IBIS at DST/NSO, EUV images and magnetograms from the SDO, coronagraph images from STEREO and the X-ray flux observations from FERMI and GOES. We establish that the filament destabilisation and eruption are the main trigger for the flaring activity. A surge-like event with a circular ribbon in one of the filament footpoints is determined as the possible trigger of the filament destabilisation. Plasma draining in this footpoint is identified as the precursor for the filament eruption. A magnetic flux emergence prior to the filament destabilisation followed by a high rate of flux cancelation of 1.34$times10^{16}$ Mx s$^{-1}$ is found during the flare activity. The flare X-ray lightcurves reveal three phases that are found to be associated with three different ribbons occurring consecutively. A kernel from each ribbon is selected and analysed. The kernel lightcurves and H alpha line profiles reveal that the emission increase in the line centre is stronger than that in the line wings. A delay of around 5-6 mins is found between the increase in the line centre and the occurrence of red asymmetry. Only red asymmetry is observed in the ribbons during the impulsive phases. Blue asymmetry is only associated with the dynamic filament.
We present high-resolution observations of two kinds of dynamic behavior in a quiescent prominence using the New Vacuum Solar Telescope, i.e., Kelvin-Helmholtz instabilities (KHIs) and small-scale oscillations. The KHIs were identified as rapidly developed vortex-like structures with counter-clockwise/clockwise rotations in the Ha red-wing images at +0.3 A, which were produced by the strong shear-flows motions on the surface/interface of prominence plumes. The KHI growth rates are estimated to be about 0.0135 +(-)0.0004 and 0.0138 +(-) 0.0004. Our observational results further suggest that the shear velocities (i.e, supersonic) of the mass flows are fast enough to produce the strong deformation of the boundary and overcome the restraining surface tension force. This flow-driven instability might play a significant role in the process of plasma transfer in solar prominences. The small-scale oscillations perpendicular to the prominence threads are observed in the Ha line-center images. The oscillatory periods changed non-monotonically and showed two changing patterns, in which one firstly decreased slowly and then it changed to increase, while the other grew fast at the beginning and then it changed to decrease. Both of these two thread oscillations with changing periods were observed to be unstable for an entire cycle, and they were local in nature. All our findings indicate that the small-scale thread oscillations could be magnetohydrodynamic waves in the solar corona.
Observations of the early rise and propagation phases of solar eruptive prominences can provide clues about the forces acting on them through the behavior of their acceleration with height. We have analyzed such an event, observed on 13 April 2010 by SWAP on PROBA2 and EUVI on STEREO. A feature at the top of the erupting prominence was identified and tracked in images from the three spacecraft. The triangulation technique was used to derive the true direction of propagation of this feature. The reconstructed points were fitted with two mathematical models: i) a power-law polynomial function and ii) a cubic smoothing spline, in order to derive the accelerations. The first model is characterized by five degrees of freedom while the second one is characterized by ten degrees of freedom. The results show that the acceleration increases smoothly and it is continuously increasing with height. We conclude that the prominence is not accelerated immediately by local reconnection but rather is swept away as part of a large-scale relaxation of the coronal magnetic field.
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